The present invention relates to a heat exchanger, and more particularly to a method of manufacturing a heat exchanger.
This application claims priority to foreign application DE 101 32 617.3 filed Jul. 5, 2001 in Germany, the contents of which are incorporated in their entirety herein by reference.
Heat exchangers having a construction as shown in EP 479 012 B1 suppress the expansion of the flat tubes caused by the internal pressure. However, such heat exchangers are expensive to produce. In particular, start up costs, including tooling, equipment, etc., necessary for large series manufacture, can be significant. Accordingly, the cost per heat exchanger increases if a limited number of heat exchangers are produced. Heat exchangers for vehicles are often designed for different cooling capacity, because customers demand vehicles of the same model with different engines. One solution for providing heat exchangers of roughly the same size, but with different cooling capacity, is to provide cooling grates with different depths. That is, flat tubes having a large major dimension are used for higher cooling capacity, while flat tubes having a smaller major dimension are used for more limited cooling capacity. However, this solution entails significant expense for new tooling and equipment. In particular, new tube bottoms and possibly even new collecting boxes, each requiring a new die, are required for each heat exchanger having a different capacity.
Accordingly, there is a need for an improved heat exchanger and method of manufacturing a heat exchanger.
The present invention enables the manufacturing of heat exchangers for a higher cooling capacity by employing a cooling grate of greater depth, while requiring only small modification and expense. Because the intermediate bottom of the heat exchangers of the present invention have an edge that is metallically joined to the peripheral edge of the tube bottom, and because the intermediate bottoms have one or more openings so that a space traversed by the heat-exchanging medium flowing through the flat tube is present between the intermediate bottoms and the corresponding tube bottom, it is possible, with limited modification expense, to make a heat exchanger having a cooling grate of greater depth, and therefore greater cooling capacity. The traversable space between the intermediate bottom and the tube bottom ensures compensation for the depth difference and for pressure differences over the length of the collecting box.
The intermediate bottom preferably has openings corresponding to the flat tube ends with passages, in order to be able to solder the flat tube ends in the passages, when the intermediate bottom is arranged beneath the corresponding tube bottom. Alternatively, the intermediate bottoms can have only one or a few openings provided with stiffening connectors when the intermediate bottom is arranged above the corresponding tube bottom.
Accordingly, the collecting boxes of the heat exchangers of the present invention with lower cooling power can be used without having to make any changes. The shaping tool for producing the tube bottom can also be used, in which no changes or only limited changes as explained below, are necessary. The only additional expense consists of preparing a die for the intermediate bottom. However, because the tolerances of the intermediate bottom are relatively minor, the required tooling expense is low. In any case, the degree of deformation of the intermediate bottom is more limited than that of the tube bottom, which also contributes to relatively low tooling costs of the intermediate bottom. The invention therefore makes it possible to lay out the dies and equipment for large series production.
Since the vehicles in a vehicle model with a lower engine power and cooling demands are often the ones that are produced in the largest numbers, the dies can be specfically made to the components required for them. For example, a heat exchanger could be made for a vehicle having a cooling grate depth of approximately 30 mm, which corresponds roughly to the major dimension of the flat tube of the cooling grate. For vehicles of the same model, but with greater engine power, more high performance heat exchangers are required in smaller numbers, and could have a cooling grate depth of approximately 40 mm.